JPH09210016A - Scale-incorporated piston rod cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a part in common and prevent the deterioration of a recording medium constituting a scale by incorporating the independent scale in a piston rod so that no special rod shape is required. SOLUTION: When an operating fluid is injected from the operating fluid inlet/outlet (a) of a rear bracket 11, a piston 20 is pressed and moved forward by the pressure. The scale gradation signal is fed to a detecting head 1 from a scale 2 incorporated in a piston rod 6. The piston 20 is provided with holes to be inserted with two guide rods 3 centering on the piston rod 6, and the movement of the piston 20 around its center axis is prevented by the guide rods 3. The scale 2 fitted in the piston rod 6 by a pressing spring 4 is moved at a constant detection gap from a magnetic head l while generating the scale signal, and the position, shift quantity, and speed of a measured object can be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston rod type cylinder in which a magnetic scale is incorporated inside a piston rod and a magnetic memory of the magnetic scale is detected by a magnetic detection head located outside the piston rod.

[0002]

Conventionally, the basic structure of a piston rod cylinder having a length measuring function is as follows. (A) The piston rod surface is magnetically plated and the scale scale is recorded on it. (B) A recording is made by forming a groove in the longitudinal direction on the surface of the piston rod, incorporating a magnetic material therein. (C) The piston rod itself is made of a magnetic material and recorded. (D) A piston rod having a comb-like groove formed in the lateral direction so as to have a magnetic change.

However, these have the following drawbacks. (A-1) It is difficult to obtain good output characteristics with the magnetic plating as described in (a) above.
Therefore, high output cannot be obtained. (A-2) Further, the environment resistance of the magnetic plating is poor, and the plating surface may be rusted or peeled off depending on use conditions. (A-3) Further, in order to apply magnetic plating, plating equipment is required in the manufacturing process, which increases the cost of the product.

(B-1) In order to incorporate the magnetic material as described in (b) above, a plastic magnet or a rubber magnet can be used as the incorporated magnetic material. When these materials are used, Since the magnetic material itself is a soft material, it will be worn out and the scale output will decrease if it is used for a long time. In addition, it is easily scratched by chips, iron powder, etc. (B-2) In the case of a hydraulic cylinder or an air cylinder containing oil, the material such as the plastic magnet or the rubber magnet sucks oil and expands, so that the movement of the cylinder is deteriorated and the scale accuracy is deteriorated.

(C-1) Although the piston rod itself can be made of a magnetic material as described in (c) above, making a medium-sized piston rod or a large-sized piston rod of a magnetic material is the current state of technological development. However, considering various problems in production, we have not yet been able to adequately deal with it. It is also necessary to consider the material (c-2) in terms of magnetic properties, wear resistance, rigidity and the like.

(D-1) As described in (d) above, although it has been considered to form comb-teeth-shaped grooves in the lateral direction of the piston rod, the comb-teeth-shaped grooves are processed at an accurate pitch. Therefore, there was a limit in obtaining a highly accurate scale. (D-2) It is necessary to match the groove of the comb tooth with the diameter of the piston rod and fill it, but depending on the material selection of this part, it may lead to troubles due to wear, chipping, etc. there were.

As described above, it can be said that the conventional methods described above all process the surface of the piston rod and create scale scales themselves. The present invention overcomes the above-mentioned drawbacks of conventional piston rods, has a long service life, and
It is an object of the present invention to provide a piston rod cylinder with a built-in scale that can be treated in the same way as a piston rod without a scale in appearance.

[0008]

In order to solve the above-mentioned problems, the piston rod cylinder according to the present invention incorporates an independent scale inside the piston rod.

To describe the specific structure, the piston rod cylinder targeted by the present invention is a fluid-driven piston rod cylinder, which is formed inside the piston rod along its longitudinal direction. The piston rod is provided with a cavity, a magnetic length measuring scale device incorporated in the cavity, and a support member for supporting the scale device, and a magnetic detection type head arranged outside the piston rod. The magnetic scale of the scale device can be detected as a magnetic signal that has passed through the material.

Since the scale is covered with a piston rod material, there is no influence of chips, oil, etc. on the scale from the outside, and the scale can be used as a piston rod cylinder that can endure the conventional use environment.

The magnetic signal emitted from the scale incorporated inside the piston rod passes through the piston rod material (preferably a non-magnetic material such as stainless alloy, aluminum alloy, copper alloy, zinc alloy, glass, ceramic, plastic) Since it has a structure that fits in the detection head, there is no need to record or scale the piston rod itself.

Further, since the scale material is not restricted to the magnetic material made of metal, and the plastic magnets and rubber magnets currently used can be used without any problems, the productivity is good and the production at low cost is possible.

According to one aspect of the present invention, in the piston rod cylinder with a built-in scale, a groove is formed in a longitudinal direction on a sidewall of a cavity formed in the longitudinal direction of the piston rod, the sidewall being close to the magnetic detection type head, It is preferable to have a structure in which a length measuring scale device is embedded in the groove.

According to another aspect of the present invention, in the above-described piston rod cylinder with built-in scale, a piston rod is provided in the cylinder in order to maintain a constant gap between the scale incorporated in the piston rod and the magnetic detection head. It is preferable that at least one guide rod is provided in parallel, or the inner shape of the cylinder and the piston are deformed to prevent rotation of the piston rod.

According to still another aspect of the present invention, in the above-described scale built-in piston rod cylinder, the supporting member uses the elastic force of a corrugated pressing spring, a pressing spring utilizing the side surface of a coil spring, rubber urethane or the like. It is preferable to use an elastic body such as a pressing spring or a pressing spring that utilizes the elasticity of plastic (resin) molding.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Next, various embodiments of the piston rod cylinder with a built-in scale of the present invention will be described. FIG. 1 is a sectional view showing the structure of a cylinder in an embodiment of a piston rod cylinder with a built-in scale according to the present invention.

As shown in the figure, the piston rod 6 is
In the present embodiment, it is configured by a hollow pipe, the inner wall of the pipe is provided with a groove along the longitudinal direction,
The scale 2 and the scale retainer 19 are installed in the groove, and they are held by being pressed against the inner wall of the pipe in the groove by the scale retainer spring 4 (support member). The scale retainer 19 is not an indispensable member and may be omitted depending on the thickness and mechanical strength of the scale.

A piston rod screw 5 is screwed to the front end of the piston rod 6. In addition, at the rear end of this piston rod 6, a lock nut 7
Is attached. Piston rod 6 and piston 2
An O-ring 17 is provided between 0 and the piston 2
There is a sealing 18 between the 0 and the cylinder 8.

The piston 20 has two holes through which the guide rods 3 pass, and the two guide rods 3 are inserted in the holes.
One end of each is inserted. These two guide rods 3 are arranged on both sides of the piston rod 6 as a center, and the other ends of the two guide rods 3 are fitted into corresponding two holes provided in the front bracket 12. The guide rods 3 prevent the piston rod 6 from rotating. An O-ring 16 is provided between the front bracket 12 and the piston rod 6, and an O-ring 21 is provided between the front bracket 12 and the cylinder 8.

The piston rod 6 is arranged so as to reciprocate in the cylinder 8 in the longitudinal direction. The piston rod 6 is aligned so as to move in the cylinder 8 along its central axis. For guide bush 9
Is provided. The guide bush 9 is provided with a dust seal 14 and a Y packing 15.

The guide bush 9 is fixed to a flange portion 10, and the magnetic head 1 is attached to the flange portion 10 from the surface of the scale 2 in accordance with a specified gap. A rear bracket is attached to the other end of the cylinder 8, and an O-ring 22 is inserted between the rear bracket 11 and the cylinder 8.

Guide bush 9, front bracket 12,
Cylinder 8 and rear bracket 11 are four bolts 1
It is attached to the flange portion 10 at 3.

Next, with reference to FIG. 2, an example of use of the scale built-in piston rod cylinder of the present invention will be described. As shown in the figure, the scale 202 built in the piston rod 203 is read by the detection head 201, sent to the detector circuit 211, and sent to the program controller 212 as signals such as A / B phase signals and SIN / COS signals.

The program controller 212 receives the detection signal relating to the movement of the piston rod sent from the detector 211, and outputs it as a position display signal to the counter 2
13 and sends a control signal for opening and closing the solenoid valve 209.

For example, in the case of positioning, when the piston rod is at a certain position, the position of that point is read, this position is used as a reference position and stored in the program controller 212, and then the program controller 2
A control signal is sent from 12 to open the solenoid valve 209, and the fluid pressure pump 210 such as hydraulic pressure or pneumatic pressure is connected to the fluid (oil etc.) inlet / outlet 207 or 208 of one of the front bracket 206 and the rear bracket 205. By sending a squeezing fluid (oil or the like) while discharging it from 208 or 207, the piston rod 203 is moved in a desired direction,
The amount of movement is measured by a scale reading device (detection head 20
1, read by the detector 211) and send it to the program controller. Program controller 2
When it is determined that the piston rod has come to the desired position, 12 outputs a control signal to close the electromagnetic valve and controls the piston rod to stop at that position.

These controls are performed automatically by using the stored data by measuring and storing the timing of the control signal, the hydraulic pressure, etc. in advance according to the operating characteristics of the piston rod 203. be able to. Functions such as calculation and judgment necessary for this control are provided in this program controller. Further, by combining with a servo valve or a sequencer, highly accurate position control becomes possible.

Next, the case of using this device for measurement will be briefly described. Since the piston rod moves from the reference position to the position of the object to be measured and is mechanically stopped there, read the value of the scale at that time. With this, it is possible to measure the position of the measurement target, the amount of movement, the speed of movement, and the like.

Next, the operation of the piston rod cylinder with a built-in scale of the present invention will be described. Referring again to FIG. 1, the front bracket 12 and the rear bracket 11 are provided with inlets and outlets a and b for the working fluid (oil or air), respectively, and these inlets and outlets are connected to the inside of the cylinder.

A piston rod 6 passes through the front bracket 12, and the front end of the piston rod 6 is
Sealed with Y packing 15, O-ring 16, etc.,
A piston 20 is attached to the other end by a lock nut 7. The piston 20 abuts on the inner wall of the cylinder, and the space on the front bracket 12 side and the rear bracket 11 side.
The space on the side is isolated.

Accordingly, when the working fluid is injected from the working fluid inlet / outlet port a of the rear bracket 11, the working fluid enters the cylinder 8 and the piston 20 is pushed by the pressure, and the piston 20 moves forward. . Along with that, the piston rod 6 integrated with the piston 20 also moves forward. At this time, a scale graduation signal is transmitted from the scale 2 built in the piston rod 6 to the detection head 1.

The piston 20 is provided with holes, through which two guide rods 3 arranged in parallel to the piston rod 6 extend, on both sides of the piston rod 6 as a center. One end penetrates these holes and the other end is planted in the front bracket.

Therefore, the guide rods 3 prevent the piston 20 from moving around its central axis. As a result, the scale 2 mounted in the piston rod 6 by the pressing spring 4 can move while generating a scale signal while maintaining a constant detection gap with respect to the detection surface of the detection head 1. Front bracket 1
The working fluid existing in the cylinder 8 exits from the inlet / outlet b of 2.

Similarly, when the working fluid enters from the inlet / outlet b, the piston 20 moves rearward in the cylinder 8 and a scale signal is produced accordingly.

Next, the detector of the piston rod cylinder with a built-in scale will be described with reference to FIG. A cavity 302 is formed in the piston rod 301 in the longitudinal direction, a groove 306 is formed in a part of the cavity along the longitudinal direction of the piston rod, and the scale 30 is provided in the groove.
3 together with the pressing plate 304, the pressing spring 3
It is held down by 05.

Recording is performed on the scale with a high magnetic force for a long wavelength, and a highly sensitive MR element is used as a device of the detection head, whereby a wide detection gap can be obtained (for example, the recording wavelength of the scale is The gap width is about 1 to 2 mm with respect to 4 mm).

The detection head has the MR element 3 on the substrate 309.
07 and a circuit component 308 including an amplifier circuit for a signal detected by the MR element are integrally attached, and a lead cable 313 for extracting a detection signal is provided on the side of the substrate 309 opposite to the MR element. It is installed. The substrate 309 is housed in the case 310, and the epoxy resin 3
It is molded with 12. With this structure, a compact detection head (sensor) having good environment resistance can be obtained.

When the recording wavelength on the scale medium (the recording medium forming the scale 303) is shortened and the resolution is increased, the output is lowered, so that the detection gap is also reduced.
In this case, as shown in FIG. 4, by cutting the piston rod above the scale 303, the scale 303 and the MR are removed.
This can be dealt with by reducing the distance between the elements 307. Further, as will be described later, this shape also has the function of preventing rotation of the piston rod because the shape of the outer peripheral surface of the piston rod is not symmetrical with respect to the central axis.

Next, the case where the diameter of the piston rod is large will be described with reference to FIG. As shown in the figure,
Since the piston rod 501 has a large diameter, the size of the cavity for accommodating the scale is much smaller than the size of the piston rod. Therefore, in order to install the scale near the detection head, the cavity must be located closer to the outer peripheral surface than the center of the piston rod 501.

The structure in which the scale 502 and the pressing plate 503 are housed in the cavity and supported by the pressing spring 504 may be the same as that described above with reference to FIGS. 3 and 4.

As is apparent from the above description, the position of the scale arranged inside the piston rod must be close to the detection head for reading the scale. However, when the piston rod rotates about its central axis, the distance between the scale and the detection head becomes large, which reduces the reliability of the detected signal. Therefore, in the piston rod cylinder of the present invention, measures for preventing the rotation of the rod have been considered.

Next, an example in which a guide rod is provided to prevent rotation of the piston rod will be described with reference to FIG. In the figure, the piston rod 601, the piston 602, the Y packings 603 and 609, the front bracket 604, the rear bracket 605, and the cylinder 606 have the same configurations as those described above, and thus detailed description thereof will be omitted.

In the example shown in FIG. 6, two guide rods 608 are provided between the front bracket 604 and the rear bracket 605. One end of each of these guide rods is fixed to the front bracket with a push screw 607. The other ends of these guide rods 608 are inserted into opposing holes provided in the rear bracket. The hole on the rear bracket side is made slightly larger than the diameter of the guide rod so that it can follow the fluctuation of the piston by the bending of the guide rod.

These guide rods 608 are arranged so as to be parallel to the piston rod, and the piston 6
02 through the hole in the rear bracket 605. Y packings 603 and 60 on both ends of the piston
9 is attached to seal the guide rod and the piston hole. This makes the piston move smoothly.

In the above description, the case where the hole for the guide rod provided in the rear bracket is formed slightly larger than the diameter of the guide rod has been described. However, in the case where a higher precision position accuracy is required. Requires improving the accuracy of the parts that make up the piston rod cylinder, and pressing the guide rod with the screws in the rear bracket as well. Although FIG. 6 shows the case where the number of guide rods is two, this guide rod is intended to prevent the rotation of the piston rod 6, so that one guide rod or three or more guide rods may be considered.

Next, with reference to FIG. 7, a case will be described in which the guide rod is not used and the internal shape of the cylinder and the piston are modified to prevent rotation. In the figure, a piston rod 701, a piston 702, a Y packing 703, a front bracket 704, and a rear bracket 70.
5, the cylinder 706 has the same configuration as that described above with reference to FIG. 6, and therefore detailed description thereof will be omitted here.

The shape of the piston 702 may be a non-circular shape, for example, an ellipse, a shape in which a part of the circle is cut, a shape in which a part of the circle is inflated, a substantially square shape, and the like. By making the shape of the piston 702 as shown and matching the shape of the cylinder 706 with the shape of the piston, rotation about the center point is prevented.

In the embodiment of the piston rod cylinder of the present invention, the scale is housed alone or together with the pressing plate in the cavity provided in the piston rod and is supported by the supporting member. As the member, various supporting members as exemplified below can be considered.

8 to 11 show examples of the supporting member. The structure of the piston rod shown in these drawings is drawn as the same structure for the sake of clarity. In addition, the internal cavity of the piston rod is provided with a groove in which a flat plate or ribbon shape (polygonal or round shape is also possible)
The description will be made assuming that the structure has a scale and a pressing plate incorporated therein.

In the piston rod of FIG. 8, the scale is fixed over the entire length by a flat plate and a corrugated holding spring via a holding plate. The holding spring may have a corrugated round bar instead of a flat plate. If the piston rod and scale and the pressure plate and scale are coated with an adhesive, they will become stronger. In addition, the environment resistance can be improved by filling the cavity inside the piston with epoxy resin (silicone, rubber-based potting material) or the like and integrating them.

FIG. 9 shows a case where a pressing spring in which a coil is connected in a corrugated shape with a round bar is used. FIG. 10 shows a case where a pressing spring using the side surface of the coil spring is used.
FIG. 11 shows a case where a pressing spring utilizing the elasticity of a rubber, urethane or plastic molded member is used.

[0051]

The scale built-in piston rod cylinder of the present invention has the following effects by having the above-mentioned structure. The outer shape of the piston rod remains the same as that of the conventional piston rod, and the recorded scale is built into the piston rod, so the rod shape can be the same as before, round shape, etc. Do not change the shape of related parts such as, seals, felts and bushes.

Further, according to this structure, since the scale is completely contained in the piston rod, the coolant,
It is not damaged by oil or chips. Further, since the scale is not exposed on the surface, it is possible to prevent the recording medium constituting the scale from being deteriorated due to the surrounding environment, and it is possible to guarantee a long life equivalent to that of a conventional piston rod having no scale.

By attaching the guide rod to the inside of the cylinder, it is possible to prevent rotation even if the piston rod remains round, so that there is an advantage that packings, bushes and the like do not have to have a special shape.

When a recorded scale device is attached to the inside of the piston rod, the bottom surface of the scale is directly or via a pressing plate and pressed by a corrugated pressing spring or the like to stop the assembly, and the assembly is easy and uniform. Since the scale can be held down with any force, it can be stopped stably for long scales. This structure is also a structure that is strong against external impact and is not easily affected by the outside.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of an example of a piston rod cylinder with a built-in scale according to the present invention.

FIG. 2 is a system configuration diagram showing an example of use of a piston rod cylinder with a built-in scale.

FIG. 3 is a cross-sectional view showing details of a scale and a detection head unit.

FIG. 4 is a cross-sectional view showing details of a scale and a detection head unit.

FIG. 5 is a cross-sectional view showing details of the scale and the detection head portion when the piston rod diameter is large.

FIG. 6 is a sectional view of a piston rod cylinder when a guide rod for preventing rotation of the piston rod is provided in the cylinder.

FIG. 7 is a cross-sectional view of a piston rod cylinder in which rotation is prevented by making the internal shape of the cylinder the same as the shape of the piston, and by making the shape not point-symmetric with respect to the center of the piston rod.

FIG. 8 is a cross-sectional view showing an example of a scale pressing spring.

FIG. 9 is a cross-sectional view showing another example of the scale pressing spring.

FIG. 10 is a cross-sectional view showing another example of the scale pressing spring.

FIG. 11 is a cross-sectional view showing another example of the scale pressing spring.

[Explanation of symbols]

1 detection head, 2 scale, 3 guide rod, 4
Scale holding spring, 5 piston rod screw, 6
Piston rod, 7 lock nut, 8 cylinder, 9
Guide bush, 10 flange, 11 rear bracket, 12 front bracket, 13 bolt

Claims (4)

[Claims] 1. A fluid-driven piston rod cylinder, wherein the piston rod has a cavity formed in the interior thereof along the longitudinal direction, and a magnetic length measuring scale device incorporated in the cavity. A magnetic detection type head provided outside the piston rod, the magnetic scale of the scale device being detected as a magnetic signal passing through the piston rod material. This is a piston rod cylinder with built-in scale. 2. The piston rod cylinder with a built-in scale according to claim 1, wherein a groove formed in the longitudinal direction of the cavity formed in the longitudinal direction of the piston rod is formed in the longitudinal direction, and the groove is formed in the longitudinal direction. A piston rod cylinder with a built-in scale, characterized by having a length measuring scale device embedded inside. 3. The piston rod cylinder with a built-in scale according to claim 1, wherein in order to keep a gap between the scale incorporated in the piston rod and the magnetic detection head constant, at least parallel to the piston rod in the cylinder. A piston with a built-in scale, characterized in that rotation of the piston rod is prevented by providing one guide rod or by making the shape of the cylinder and the piston substantially the same and not circular. Rod cylinder. 4. The scale built-in piston rod cylinder according to claim 1, wherein the supporting member is a corrugated pressing spring, a pressing spring using a side surface of a coil spring, a pressing spring using elastic force such as rubber urethane, and a plastic. (Resin) A piston rod cylinder with a built-in scale, which is made of an elastic body such as a pressing spring that uses the elasticity of molding.